JP2015163726A - Method of producing nickel powder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nickel powder which is produced by a wet method, has a small average grain size and a uniform grain size distribution without increasing the content of a metal more precious than the expensive nickel and is reduced in connection particles and coarse particles.SOLUTION: A nickel powder is produced by a wet method based on precipitating nickel by using a colloidal solution dispersed with composite colloidal particles containing a salt of a metal more precious than nickel, a protective colloid agent and a reductant, a complexing agent, an alkaline substance and an aqueous solution of a nickel salt, contains a hydroxycarboxylic acid and an organic acid having at least one carboxyl group as a complexing agent, in a molar ratio of the hydroxycarboxylic acid to the organic acid corresponding to 50-95% of the hydroxycarboxylic acid.

Description

  The present invention relates to nickel powder and a method for producing the same, and is used, for example, as an internal electrode of a multilayer ceramic capacitor.

  Nickel powder is used as a material for a conductive paste for producing a thick film conductor. The thick film conductor is used for forming an electric circuit, an electrode of a multilayer ceramic component such as a multilayer ceramic capacitor (MLCC), a multilayer ceramic substrate, or the like.

  In recent years, the size and capacity of monolithic ceramic capacitors have increased, and the amount of conductive paste used for monolithic ceramic capacitors has also increased significantly. For this reason, as the metal powder used for the conductive paste, the use of expensive noble metals is avoided, and inexpensive base metals such as nickel are mainly used.

  A multilayer ceramic capacitor, which is a multilayer ceramic component, is manufactured as follows. In the method for manufacturing a multilayer ceramic capacitor, a conductive paste kneaded with a nickel powder, a resin such as ethyl cellulose, an organic solvent such as terpineol, etc. is screen-printed on a dielectric green sheet. The dielectric green sheets on which the conductive paste is printed are laminated and pressure-bonded so that the conductive pastes are alternately stacked.

  In the laminated body in which the dielectric green sheet is pressure-bonded, it is cut into a predetermined size, and a resin such as ethyl cellulose used as an organic binder is removed by combustion (debinder treatment), and the ceramic body is fired at a high temperature at 1300 ° C. can get. In the method for manufacturing a multilayer ceramic capacitor, an external electrode is attached to the obtained ceramic body to obtain a multilayer ceramic capacitor.

  Since the base metal such as nickel is more prevalent than the precious metal for the metal powder in the conductive paste to be the internal electrode, a very small amount of oxygen is used in the debinding process of the laminate so that the nickel powder does not oxidize. It is performed in an atmosphere that includes it.

  In recent years, there has been a demand for a monolithic ceramic capacitor having a smaller size and a larger capacity, and a thinner layer is being promoted together with internal electrodes and dielectrics. In particular, the particle size of nickel powder used for the internal electrode is mainly 0.5 μm or less.

  The nickel powder used for the internal electrode is required to have various characteristics, one of which is required not to include coarse particles. The reason is that if the nickel powder contains coarse particles, the coarse particles protrude from the internal electrode layer, and contact with another internal electrode layer causes a short circuit.

  As a method for obtaining nickel powder that does not contain coarse particles, there is a method of removing coarse particles by classification after crystallization of nickel powder. For example, Patent Document 1 slurries nickel powder using water as a medium, A method has been proposed in which coarse particles of 2 μm or more are suppressed to 100 parts per million or less by classification with a hydrocyclone.

  On the other hand, as a method for obtaining nickel powder containing no coarse particles, for example, Patent Document 2 discloses that average particle size is obtained by precipitating nickel powder using a colloidal solution in which composite colloidal particles composed of palladium and silver are dispersed. There has been proposed a method for obtaining a spherical nickel powder having a small diameter, a uniform particle size distribution, good dispersibility, and few coarse particles and connecting particles.

  In Patent Document 2, in order to obtain nickel powder having a finer average particle size, a uniform particle size distribution, and coarse particles and connected particles, the concentration of palladium and silver, which are noble metal components of colloidal particles, is set. It is said that raising it is effective.

JP 2001-62332 A JP 2007-138291 A

  However, the method described in Patent Document 1 is a method in which a classification step is added, and in addition to the coarse particles removed by classification, factors that reduce the yield for reasons such as adhesion of slurry to the apparatus Thus, there is a disadvantage that the manufacturing cost increases. Further, the method described in Patent Document 1 has a drawback that classification itself becomes difficult when the particle size of the nickel powder is 0.2 μm or less, particularly 0.1 μm or less.

  When using a noble metal like patent document 2, since the price of a noble metal is expensive compared with a nickel price, it will be accompanied by the increase in manufacturing cost.

  Accordingly, an object of the present invention is to provide a nickel powder production method suitable for producing an internal electrode of a thin-film multilayer ceramic capacitor, for example, without increasing the production cost. It is to provide. Specifically, in the wet method, production of nickel powder having a small average particle size, uniform particle size distribution, and fewer connected particles and coarse particles without increasing the concentration of noble metal than expensive nickel It is to provide a method.

  As a result of intensive studies to achieve the above object, the inventors of the present invention have prepared, as a complexing agent, at least a hydroxycarboxylic acid as a complexing agent in a wet method using a metal salt noble from nickel. It has been found that the above problem can be solved by combining with an organic acid containing one or more carboxyl groups.

  In order to achieve the above-mentioned object, a method for producing nickel powder according to the present invention includes a colloidal solution in which composite colloidal particles containing a metal salt noble than nickel, a protective colloid agent, and a reducing agent are dispersed, and complexed. A nickel powder production method using a wet method in which nickel is precipitated by an agent, an alkaline substance, and an aqueous nickel salt solution, wherein the complexing agent comprises a hydroxycarboxylic acid and an organic acid containing at least one carboxyl group The ratio of the hydroxycarboxylic acid and the organic acid is characterized in that the hydroxycarboxylic acid is in a molar ratio of 50% to 95%.

  According to the present invention, it is possible to produce a nickel powder having a uniform particle size distribution and a small number of connected particles and coarse particles, without increasing the concentration of noble metal than nickel. .

  Moreover, according to this invention, since it can provide without increasing the manufacturing cost of nickel powder, the industrial value is very large.

  Furthermore, according to the present invention, nickel powder that is particularly suitable for the internal electrode of a thin-film multilayer ceramic capacitor can be produced as a member of the multilayer ceramic capacitor.

4 is a SEM photograph of nickel powder obtained in Conventional Example 1. 6 is a SEM photograph of nickel powder obtained in Example 5. 4 is a SEM photograph of nickel powder obtained in Conventional Example 2. 4 is a SEM photograph of nickel powder obtained in Example 9.

  Hereinafter, the nickel powder and the manufacturing method thereof (hereinafter referred to as “the present invention”) according to the present invention will be described in detail along the following items. Note that the present invention is not limited to the following embodiments, and various modifications can be made without departing from the scope of the present invention.

1. 1. Manufacturing method of nickel powder 1-1. Preparation of colloidal solution 1-2. Precipitation of nickel powder 1-3. 1. Drying of nickel powder Nickel powder

1. First, a method for producing nickel powder according to the present invention (hereinafter referred to as “the present production method”) will be described. In this production method, a colloidal solution in which composite colloidal particles containing a metal salt precious than nickel, a protective colloid agent, and a reducing agent for colloid preparation are dispersed, a complexing agent, an alkaline substance, and an aqueous nickel salt solution And a wet method for precipitating nickel. Hereinafter, the details of the production method will be described.

1-1. Preparation of a colloidal solution In the colloidal solution, a colloidal solution is prepared using pure water, a protective colloid agent, a reducing agent for colloid production, and a salt of a metal nobler than nickel.

(1) Protective colloid agent A colloidal solution is added with a protective colloid agent in order to suppress aggregation of colloidal particles. The protective colloid agent may be a composite colloidal particle containing a metal salt nobler than nickel, which will be described later, for example, a composite colloidal particle containing palladium and silver, and can contribute to the formation of a protective colloid. In particular, gelatin is particularly preferable. As the protective colloid agent, in addition to gelatin, protective colloid agents such as polyvinylpyrrolidone, gum arabic, sodium hexametaphosphate, polyvinyl alcohol and the like can be used.

(2) Reducing agent for colloid preparation The reducing agent for colloid preparation is not particularly limited, and is selected from, for example, hydrazine (N ₂ H ₄ ), hydrazine compounds, sodium borohydride (NaBH ₄ ), and the like. At least one kind selected can be selected as appropriate. Of these, a water-soluble hydrazine compound is preferable as the reducing agent for preparing the colloid, and hydrazine is most preferably used because it has few impurities. Moreover, the selected reducing agent for producing colloid can be used by dissolving in a solvent such as water or pure water. For example, it is preferable to use an aqueous hydrazine solution obtained by dissolving a hydrazine compound in water or pure water.

(3) Metal salt noble than nickel Examples of metal salt noble than nickel include water-soluble salts such as gold salt, silver salt, platinum salt, palladium salt, rhodium salt, iridium salt and copper salt. Among these, in particular, either a palladium salt or a silver salt, or a mixture thereof is suitable. As the metal salt nobler than nickel, it is optimal to use a solution in which a palladium salt and a silver salt are mixed in a solvent such as water or pure water. The reason is that aggregation of noble metal species that act as nuclei is suppressed. As a result, the formation of coarse particles and connected particles of nickel powder can be suppressed.

  The palladium salt is not particularly limited, and for example, at least one selected from palladium chloride, palladium nitrate, palladium sulfate and the like can be appropriately selected. Of these, palladium chloride is most preferably used as the palladium salt because of its easy liquid preparation. The selected palladium salt can be used as a palladium salt solution mixed with a solvent such as water or pure water. Moreover, as a silver salt solution etc. mixed with solvents, such as water and a pure water, silver nitrate aqueous solution can be used, for example.

(4) Mixing ratio of the colloid solution component Gelatin as a protective colloid agent, hydrazine as a reducing agent for colloid preparation, palladium salt and silver salt as noble metal salts than nickel, which are particularly suitable as raw materials for colloid solutions The blending ratio is as follows: the nickel mass in the nickel salt aqueous solution is 100%, gelatin is 0.025 mass% to 0.2 mass%, hydrazine is 0.1 mass% to 0.8 mass%, It is desirable that the amount of palladium is 10 mass ppm to 350 mass ppm, and the amount of silver in the silver salt is 0.01 mass ppm to 0.35 mass ppm.

  When the gelatin is less than 0.025% by mass, the amount of protective colloid agent is insufficient, and when the gelatin is more than 0.2% by mass, the reduction precipitation of nickel is hindered and unreduced nickel. Will occur.

(5) Procedures and conditions for colloidal solution preparation Colloidal solutions containing composite colloidal particles of metals nobler than nickel are prepared by adding a colloidal reducing agent to an aqueous solution in which a protective colloid agent is added to pure water, and nobleer than nickel. It can produce by adding the solution which mixed the salt of the various metal in any order.

  In particular, it is desirable to add a reducing agent for colloid preparation after adding a solution in which a salt of a metal nobler than nickel is added to an aqueous solution to which a protective colloid agent is added. The reason is that by adding a reducing agent for colloid preparation, a system in which noble metal species are dispersed in a finer state than nickel can be obtained, and as a result, nickel powder can be obtained with a small amount of noble metal species. This is because it can be miniaturized.

  When preparing the colloidal solution, it is desirable that the aqueous solution of the protective colloid agent before adding the metal salt nobler than nickel and the reducing agent for colloid preparation be stirred as much as possible. The reason for stirring as much as possible is that when not sufficiently stirred, fine nuclei cannot be obtained, and the particle size of the nickel powder cannot be controlled at a desired level.

  As for the temperature of the solution at the time of producing a colloidal solution, 50 to 95 degreeC is desirable. The reason for heating is that the polymer chain intertwined with the protective colloid agent gelatin is broken and the desired protective colloid effect is easily exhibited.

1-2. Nickel powder deposition Nickel powder deposition involves solid-liquid separation after nickel reduction using the resulting colloidal solution, complexing agent, alkaline substance, reducing agent, and aqueous nickel salt solution. A solid containing nickel powder is obtained.

(1) Complexing agent Any complexing agent may be used as long as it has an effect of forming a complex with nickel, and includes a hydroxycarboxylic acid and an organic acid containing at least one carboxyl group. As the hydroxycarboxylic acid, tartaric acid, citric acid, malic acid and ascorbic acid are preferable, and tartaric acid is more preferable. As the organic acid containing a carboxyl group, saturated fatty acid, dicarboxylic acid, oxocarboxylic acid and amino acid are preferable, and formic acid, acetic acid, pyruvic acid and glycine are more preferable.

  As the complexing agent, the hydroxycarboxylic acid and the organic acid having at least one carboxyl group may be each a single component or a mixture of two or more components. The reason for including a hydroxycarboxylic acid and an organic acid containing at least one or more carboxyl groups as a complexing agent is that, according to the inclusion of these, in the presence of a colloidal solution containing fine nuclei, This is because by forming a nickel complex in which a carboxylic acid and an organic acid containing a carboxyl group are mixed, a nickel powder having a fine particle size, a narrow particle size distribution, a small number of connected particles, and a good sphericity can be obtained. .

  Among the complexing agents, the ratio of the hydroxycarboxylic acid to the organic acid containing at least one or more carboxyl groups is 50% to 95%, more preferably 60% to 90%, in terms of molar ratio. To do.

  If the ratio of the hydroxycarboxylic acid is less than 50% in terms of molar ratio, the effect of reducing the particle size or reducing the standard deviation of the particle size may not be exhibited. Moreover, when the ratio of hydroxycarboxylic acid exceeds 95% in molar ratio, the effect of adding an organic acid containing at least one or more carboxyl groups may not be exhibited.

(2) Alkaline substance Although it does not specifically limit as an alkaline substance, For example, water-soluble alkaline substances, such as sodium hydroxide, potassium hydroxide, and ammonia, are desirable. Moreover, the alkaline hydrazine aqueous solution can be prepared by mixing these water-soluble alkaline substances and a reducing agent described later in pure water.

(3) Reducing agent The reducing agent is not particularly limited, and for example, the same reducing agent as that for colloid preparation described above can be used.

(4) Nickel salt aqueous solution The nickel salt aqueous solution is not particularly limited, and for example, an aqueous solution containing at least one kind of nickel salt selected from nickel chloride, nickel nitrate, nickel sulfate and the like can be used. Among these aqueous solutions, an aqueous nickel chloride solution or an aqueous nickel sulfate solution is preferable, and an aqueous nickel chloride solution that can be easily treated with a waste liquid is particularly preferable.

(5) Nickel powder precipitation procedure and conditions As the mixing order of the colloidal solution, complexing agent, alkaline substance and reducing agent, a solution in which the colloidal solution, complexing agent, alkaline substance and reducing agent are mixed can be obtained. There is no particular limitation. For example, a complexing agent, a reducing agent, and an alkaline substance may be sequentially mixed in the colloid solution, or a solution in which a complexing agent, an alkaline substance, and a reducing agent are mixed in advance and a colloidal solution may be mixed.

  The nickel salt aqueous solution is preferably added after preparing a solution in which a colloidal solution, a complexing agent, an alkaline substance and a reducing agent are mixed. The reason is that if a solution containing a colloidal solution, complexing agent, alkaline substance and reducing agent is prepared and a nickel salt aqueous solution is not added, a monodispersed and spherical nickel powder cannot be obtained. This is because the shape of the nickel powder increases and the number of connected particles increases.

  In precipitation of nickel powder, the pH of the solution in which the colloidal solution, complexing agent, alkaline substance and reducing agent are mixed is preferably 10 or more. In this production method, when the pH is less than 10, the reaction rate is slow, and therefore, nickel is not preferable because reduction precipitation of nickel hardly occurs.

  In precipitation of nickel powder, it is desirable that the temperature before adding the nickel salt aqueous solution to the solution obtained by mixing the colloidal solution, complexing agent, alkaline substance and reducing agent is 60 ° C to 95 ° C. In the precipitation of nickel powder, the temperature of the aqueous nickel salt solution before adding to the mixed solution of the colloidal solution, complexing agent, alkaline substance and reducing agent is also preferably 60 ° C to 95 ° C.

  In the precipitation of nickel powder, it is desirable to heat the mixed solution to 70 ° C. or higher after mixing the colloidal solution, complexing agent, alkaline substance, and reducing agent mixed solution and the nickel salt aqueous solution. In this production method, the reason for heating these solutions is to proceed the reaction smoothly and obtain uniform nickel particles.

1-3. Drying of nickel powder The solid content containing the obtained nickel powder is dried to obtain nickel powder. Here, drying of the solid content containing nickel powder may employ a known method, and can be performed, for example, in a vacuum or in an inert gas atmosphere.

2. Next, the nickel powder obtained from the method for producing nickel powder according to the present invention will be described.

  The nickel powder is a nickel powder having an average particle size of 50 nm to 300 nm. Moreover, since nickel powder has a uniform particle size distribution, the standard deviation of the particle size is small and is 40 nm or less, preferably 30 nm.

  In this production method as described above, nickel powder having an average particle size of 50 nm to 300 nm, a uniform particle size distribution, and a small standard deviation of the particle size is 40 nm or less can be produced. The obtained nickel powder can be made finer in average particle size without increasing the concentration of noble metal than nickel, has a uniform particle size distribution, and can reduce the number of connected particles and coarse particles.

  In this manufacturing method, particularly when the obtained nickel powder is used in a multilayer ceramic capacitor, nickel powder suitable as an internal electrode of a thin-film multilayer ceramic capacitor is provided without increasing the manufacturing cost. Can do.

  Since this manufacturing method can be provided without increasing the manufacturing cost of nickel powder, its industrial value is extremely high.

  Hereinafter, the present invention will be described in more detail with reference to each of Examples and Conventional Examples, but the present invention is not limited to these Examples and Conventional Examples. In addition, the evaluation method of the average particle diameter of the nickel powder obtained by the Example and the conventional example, the standard deviation of a particle diameter, and the number of coarse particles is as follows.

  The average particle diameter of the nickel powder was taken using a scanning electron microscope (SEM: Scanning Electron Microscope, manufactured by JEOL Ltd., JSM-5510) at a magnification of 20000 times (length: 19.2 μm × width: 25.6 μm). Then, the area of the particles where the entire shape of the particles in the photograph can be seen was measured, the radius of each particle was determined from the area, and the average value was determined.

  The standard deviation of the particle diameter of the nickel powder is measured in the same manner as the average particle diameter described above, by measuring the area of the particles where the entire shape of the particles in the SEM photograph can be seen, and determining the radius of each particle from the area. Determined.

  The number of coarse particles of the nickel powder is the same as the average particle size described above, the area of the particles in which the entire shape of the particles in the SEM photograph can be seen is measured, the radius of each particle is obtained from the area, and the particle size is 500 nm. The number of particles was larger. In addition, about the connection particle | grain, the maximum diameter was considered as a diameter, and when this diameter was larger than 500 nm, it handled as a coarse particle.

(Conventional example 1)
In Conventional Example 1, gelatin was dissolved in 6.5 L of pure water at 75 ° C. so that the amount of gelatin was 0.025 mass% with respect to the total mass of nickel in the nickel salt aqueous solution to be added later. An aqueous solution prepared by mixing an aqueous palladium chloride solution and an aqueous silver nitrate solution was added so that palladium was 25 ppm by mass and silver was 0.025 ppm by mass with respect to the total mass, and a colloidal solution was obtained while stirring.

  In Conventional Example 1, 8 g of tartaric acid, which is a complexing agent, is added to the obtained colloidal solution, the pH of the aqueous sodium hydroxide solution is adjusted to 10 or more, and 200 mL of 60 vol% hydrazine that is a reducing agent is added. Thereafter, 500 mL of a nickel chloride aqueous solution having a nickel concentration of 100 g / L was mixed to reduce nickel, followed by solid-liquid separation in an inert gas atmosphere.

  In Conventional Example 1, the separated solid content is dried in a vacuum dryer, and heat-treated at a heating temperature of 180 ° C. and a heating time of 60 minutes in a hydrogen-nitrogen mixed gas atmosphere having a hydrogen concentration of 2.0 vol%, Obtained.

  In Conventional Example 1, the obtained nickel powder was treated with a spiral jet mill (manufactured by POWREC Co., Ltd.). In Conventional Example 1, the processing conditions of the spiral jet mill were as follows: the pulverization pressure was 0.50 MPa, the supply pressure was 0.55 MPa, the powder supply amount was 50 g / min, and the gas medium was air.

  In Conventional Example 1, the average particle diameter of the obtained nickel powder, the standard deviation of the particle diameter, and the number of coarse particles were evaluated, and the evaluation results are shown in Table 1 and FIG.

Example 1
In Example 1, X% of 8 g of tartaric acid as a complexing agent was weighed, and the remaining Y = 100-X (%) was replaced with formic acid equivalent to 8 × Y (g) of tartaric acid. Except for this, nickel powder was obtained in the same manner as in Conventional Example 1.

  In Example 1, the average particle size, standard deviation of particle size, and number of coarse particles of the obtained nickel powder were evaluated, and the evaluation results are shown in Table 1.

(Example 2)
In Example 2, X% of 8 g of tartaric acid, which is a complexing agent, was weighed, and the remaining Y = 100-X (%) was replaced with oxalic acid equivalent to 8 × Y (g) of tartaric acid. Except for the above, nickel powder was obtained in the same manner as in Conventional Example 1.

  In Example 2, the average particle size, standard deviation of particle size, and number of coarse particles of the obtained nickel powder were evaluated, and the evaluation results are shown in Table 1.

(Example 3)
In Example 3, X% in 8 g of tartaric acid as a complexing agent was weighed, and the remaining Y = 100-X (%) was replaced with pyruvic acid having an equimolar equivalent to 8 × Y (g) tartaric acid. Except for the above, nickel powder was obtained in the same manner as in Conventional Example 1.

  In Example 3, the average particle size, standard deviation of particle size, and number of coarse particles of the obtained nickel powder were evaluated, and the evaluation results are shown in Table 1.

Example 4
In Example 4, tartaric acid as a complexing agent was weighed in 8% of X%, and the remaining Y = 100-X (%) was replaced with glycine having an equimolar equivalent to 8 × Y (g) of tartaric acid. Except for this, nickel powder was obtained in the same manner as in Conventional Example 1.

  In Example 4, the average particle diameter of the obtained nickel powder, the standard deviation of the particle diameter, and the number of coarse particles were evaluated, and the evaluation results are shown in Table 1.

(Example 5)
In Example 5, X% of 8 g of tartaric acid as a complexing agent was weighed, and the remaining Y = 100-X (%) was replaced with glycine having an equimolar equivalent to 8 × Y (g) of tartaric acid. Except for this, nickel powder was obtained in the same manner as in Conventional Example 1.

  In Example 5, the average particle size, standard deviation of particle size, and number of coarse particles of the obtained nickel powder were evaluated, and the evaluation results are shown in Table 1 and FIG.

(Example 6)
In Example 6, tartaric acid as a complexing agent was weighed in 8% of X%, and the remaining Y = 100-X (%) was replaced with glycine having an equimolar equivalent to 8 × Y (g) of tartaric acid. Except for this, nickel powder was obtained in the same manner as in Conventional Example 1.

  In Example 6, the average particle diameter of the obtained nickel powder, the standard deviation of the particle diameter, and the number of coarse particles were evaluated, and the evaluation results are shown in Table 1.

(Example 7)
In Example 7, 8 g of tartaric acid as a complexing agent was changed to 10.24 g of citric acid having an equimolar amount, and X% in 10.24 g of citric acid was weighed, and the remaining Y = 100−X ( %) Was replaced with glycine having an equimolar equivalent to 10.24 × Y (g) of tartaric acid to obtain nickel powder in the same manner as in Conventional Example 1.

  In Example 7, the average particle size of the obtained nickel powder, the standard deviation of the particle size, and the number of coarse particles were evaluated, and the evaluation results are shown in Table 1.

(Conventional example 2)
In Conventional Example 2, nickel powder was obtained in the same manner as in Conventional Example 1 except that the nickel chloride aqueous solution having a nickel concentration of 100 g / L in Conventional Example 1 was replaced with nickel sulfate.

  In Conventional Example 2, the average particle size of the obtained nickel powder, the standard deviation of the particle size, and the number of coarse particles were evaluated, and the evaluation results are shown in Table 1 and FIG.

(Example 8)
In Example 8, tartaric acid as a complexing agent was weighed in 8% of X%, and the remaining Y = 100-X (%) was replaced with acetic acid equivalent to 8 × Y (g) of tartaric acid. Except for this, nickel powder was obtained in the same manner as in Conventional Example 2.

  In Example 8, the average particle size, standard deviation of particle size, and number of coarse particles of the obtained nickel powder were evaluated, and the evaluation results are shown in Table 1.

Example 9
In Example 9, X% of 8 g of tartaric acid as a complexing agent was weighed, and the remaining Y = 100-X (%) was replaced with pyruvic acid equivalent to 8 × Y (g) of tartaric acid. Except for the above, nickel powder was obtained in the same manner as in Conventional Example 2.

  In Example 9, the average particle diameter of the obtained nickel powder, the standard deviation of the particle diameter, and the number of coarse particles were evaluated, and the evaluation results are shown in Table 1 and FIG.

(Example 10)
In Example 10, tartaric acid as a complexing agent was weighed in X% in 8 g, and the remaining Y = 100−X (%) was replaced with glycine having an equimolar equivalent to 8 × Y (g) tartaric acid. Except for this, nickel powder was obtained in the same manner as in Conventional Example 2.

  In Example 10, the average particle diameter of the obtained nickel powder, the standard deviation of the particle diameter, and the number of coarse particles were evaluated, and the evaluation results are shown in Table 1.

  As shown in Table 1 and FIGS. 1 to 4, in Examples 1 to 10, a part of the complexing agent is tartaric acid, citric acid (X: hydroxycarboxylic acid) to acetic acid, formic acid, oxalic acid, pyruvic acid, or By replacing each with glycine (Y: mixed species), the ratio of X and Y being a molar ratio and X being 50% to 95%, compared to Conventional Example 1 and Conventional Example 2, palladium and It can be seen that the average particle size can be reduced to 50 nm to 300 nm without increasing the silver concentration, the standard deviation of the particle size can be reduced to 40 nm or less, and the number of coarse particles can be equal or less or less.

  As a result, the nickel powders of Examples 1 to 10 had a uniform particle size by reducing the average particle size without increasing the concentration of an aqueous solution obtained by mixing an aqueous palladium chloride solution and an aqueous silver nitrate solution, which are noble metals than nickel. In addition to having a distribution, it is possible to reduce the number of connected particles and coarse particles, and it is possible to provide nickel powder suitable for the internal electrode of a thin-film multilayer ceramic capacitor without increasing the manufacturing cost. It has a great effect.

Claims (10)

A wet method in which nickel is precipitated by a colloidal solution in which composite colloidal particles containing a metal salt noble than nickel, a protective colloid agent, and a reducing agent are dispersed, a complexing agent, an alkaline substance, and an aqueous nickel salt solution. A method for producing the nickel powder used,
The complexing agent contains a hydroxycarboxylic acid and an organic acid containing at least one carboxyl group, and the ratio of the hydroxycarboxylic acid to the organic acid is such that the hydroxycarboxylic acid has a molar ratio of 50% to 50%. A method for producing nickel powder, characterized by being 95%.   2. The method for producing nickel powder according to claim 1, wherein the hydroxycarboxylic acid is at least one selected from tartaric acid, citric acid, malic acid, and ascorbic acid.   The method for producing nickel powder according to claim 1 or 2, wherein the hydroxycarboxylic acid is tartaric acid.   The organic acid containing at least one or more carboxyl groups is one or more selected from saturated fatty acids, dicarboxylic acids, oxocarboxylic acids, and amino acids. Of manufacturing nickel powder.   5. The nickel powder according to claim 1, wherein the organic acid containing at least one carboxyl group is at least one selected from formic acid, acetic acid, pyruvic acid, and glycine. Manufacturing method.   6. The method for producing nickel powder according to any one of claims 1 to 5, wherein the metal salt nobler than nickel contains a palladium salt and a silver salt.   The method for producing nickel powder according to any one of claims 1 to 6, wherein the aqueous nickel salt solution is an aqueous solution containing at least one selected from nickel chloride and nickel sulfate.   The method for producing nickel powder according to claim 1, wherein the aqueous nickel salt solution is nickel chloride.   The nickel powder manufacturing method according to claim 1, wherein an average particle diameter of the nickel powder is 50 nm to 300 nm.   The nickel powder manufacturing method according to claim 1, wherein a standard deviation of the particle diameter of the nickel powder is 40 nm or less.